Heater with vertically extended tubes in convection section



Feb. 18, 1964 M. A. ZIMMERMAN 3,121,420

HEATER WITH VERTTCALLT EXTENDED TUBES TN coNvEcTToN SECTION Filed April 30, 1962 Figure ATTO NEYS United States Patent O 3,121,420 HEATER WITH VER'E'CALLY EXTENDED TUBES EN CNVECTEN SECTON Merle A. Zimmerman, Shreveport, La., assignor to Universal @il Products Company, Des Plaines, lll., a corporation ci Delaware Filed Apr. Sti, 1962, Ser. No. 191,090

4 tlaims. (Cl. 122-356) The present invention relates to an improved type of fluid heater construction which utilizes vertically extended radiant tubes to provide vertical tube segments within the convection heating section and, in particular, provides means `for air cooling an -inner shell or partitioning means that forms the inner wall portion of the convection section. 'The modified convection heating section and air cooling arrangement is particularly adapted for use with cylindrical vertical tube type of heaters although it may well be used in connection fwith small rectangular or box-shaped heaters having vertical tube banks.

The usual cylindrical heater constructions have vertical tubes in the lower radiant heating section and a horizontal tube bank in the upper convection section, however, such designs are expensive and unsatisfactory by reason of the necessity `for short tube lengths and a large number of return bends or headers at the ends of the tubes in the convection section and resulting large pressure drops. Other circular heater designs which use extended vertical tubes within an upper convection port-ion or" the heater generally incorporate cone baffles, and the like, to deflect hot combustion gases radially outwardly toward the tubes, but because of high temperature conditions necessarily use expensive high temperature resistant alloys in such instances. Also, in connection with cone deiiectors `and other conventional internal baffling arrangements the hot convection gases have not been efficiently channeled upwardly around the vertical tube sect-ions in insulated zones to obtain the best heat conservation and transfer relationships.

lt is, therefore, a principal object of the present invention to provide -an improved heater construction which utilizes insulated internal hollow shell means to effect partitioning means that forms a n-arrow annular convection section, or segmental sections, to accommodate one or more rows of vertically extending convection tubes positioned adjacent the inside wall of the heating chamber. Y

It -is also an object of the present invention to provide an improved construction which has air ducts extending radially inward from the outside of the heater housing to the interior of the internal convection section partitioning means so that the latter is cooled and expensive alloy materials `are unnecessary.

Briey, in one embodiment, the improved heater of this invention comprises in combination, a confined vcrtically positioned heating chamber having a ue gas outlet stack from the upper end thereof, a plurality' of vertically positioned uid conduits positioned around and `adjacent to the interior wall of the heating chamber, means connecting said conduits into at least one bank with fluid inlet and outlet means connecting thereto whereby at least one fluid stream may be heated within said chamber, heat supply means connecting with the lower end of said chamber `and introducing flame and hot gases into the interior thereof, a transverse partitioning means with superimposed vertically extending inner shell means positioned within the interior of said heating chamber and dividing said chamber into a lower radiant heating section and an open-topped annularform convection heating section, said superimposed shell means being positioned concentrically adjacent to and inwardly Ifrom the fluid conduits and forming thereby narrow gas passageway means in said convection section, an upper transverse closure member -across the top end ot said inner shell means and providing a hollow interior therefor separated lfrom the top portion of said heating chamber and from llue gases passing therethrough from the open top of said `convection section to the lue gas outlet stack, and air duct means extending radially between the outside surface of said heating chamber and the interior of said inner shell means whereby outside air is admitted to the interior of the latter.

In a preferred embodiment, the face of the inner shell which defines the convection heating section, or sections, is insulated to preclude the transfer of heat from the hot convection section into the hollow interior portion of the inner shell means. The air duct means which extend between the outside of the heater chamber and the interior of the inner shell partitioning means may comprise a multiplicity of small tube-like members positioned between the vertically positioned fluid conduits and spaced around the periphery of the heater so as to provide an adequate ow of air into `and through the hollow inner shell means. Alternatively, the air duct means to the hollow inner shell may comprise a smaller number of larger air ducts or passageways between spaced banks of vertical tubes; however, the openings should be spaced to provide a substantially uniform inward iow, or a cross liow of outside air, so as to obtain substantiallyI equalized cooling around the internal periphery of the shell. Small air duct means may have one row thereof spaced one above another so as to obtain a draft or rising air current ow arrangement through the interior portion of the heater. The spaced air duct means may also be in the form of vertically' elongated slots such that the a-ir readily enters into and circulates through the yfull height of the interior shell means.

ln still another modication small holes or apertures may be made in the top closure member of the hollow interior partitioning means to permit air liow upwardly therefrom into the outlet stack, along with. the llue gas stream, and in turn induce an inward air tlow through the ducts into the central hollow section from outside the heating chamber.

Reference to the accompanying drawings and the following descriptions thereof will serve to illustrate the improved construction features and further advantages to be obtained thereby.

FIGURE l of the drawing is a diagrammatic elevational view, partially in section, of a cylindrical form of heater having vertically positioned luid conduits and cooling air duct means extending into the interior of internal partitioning means.

FGURE 2 of the drawing is a partial sectional plan view through the heater, as indicted by the line 2-2 in FIGURE l.

FIGURE 3 of the drawing indicates a partial sectional plan view of a modified cylindrical heater design having three relatively large vertically elongated air ducts to the interior of internal partitioning means of the heater.

FIGURE 4 of the drawing is a partial sectional elevational view of the modified heater construction having the vertically elongated air passageways to the interior of the inner shell means, as shown by the line 4-4 in PlGURE 3.

Referring now to FIGURES l and 2 of the drawing, there is shown a vertical cylindrical form of fluid heater having the main chamber portion formed of shell 1 with interior insulation 2, and a sloping upward chamber portion formed of conical shell section 3 with insulation 4. An upper iiue gas outlet stack S is superimposed on the top of the chamber. A plurality of spaced burners 6 provide for the introduction of high temperature ilame and gases to the lower inner portion of the heating chamber and radiant heating to the lower portions or fluid conduits 7 positioned around and adjacent to the interior wall of the heater.

As best shown in FIGURE 2 of the drawing, the vertically disposed tubes or iiuid conduits 7 are arranged in four similar tube bank arrangements, however, the draw; ing is diagrammatic and it is not intended to limit the present improved heater construction to any one tube bankdesign or iiu'id flow into and through the various tubes. It is, however, a particular feature of the present construction and arrangement to have the vertical tubes extend upward from a lower radiant section S to an upper convection section 9. Thus, the vertical upper portions of each of the tube members provides, in effect, a convection tube bank for the heater.

A transverse partitioning plate l0, with extension portions 11 connecting to the external shell l, provides means for separating and defining the lower radiant heat'- ing section 8, as well as means for detlecting and channeling the hot combustion gases from the burners 6 to the convection section 9 and around the upper end portions of tubes 7. Superirnposed above the transverse partition 10 is a substantially continuous cylindrically shaped inner shell member 12 having an exterior layer of insulation 13 which serves toprovide an inner wall for the convection section 9 and vertically elongated narrow passageways for the flue gases passing around the upper portions of tubes 7 in the convection section. The annular-from convection section 9 is open-topped such that the hue gas stream passes into an upper gas collection zone 14 and thence passes upwardly and outwardly through the stack 5. Damper control means 15 within the lower portion of stack 5 provides for the control of the flue gas flow upwardly through the heating chamber.

An vupper transverse closure member 16, with insulation 17, encloses and forms a hollow interior portion above the transverse partitioning member 16 and within the cylindrical shell member 12, while at the same time precluding tlue gas iiow inwardly from the upper portion of the heating chamber. However, in accordance with the improved construction of the present invention, a plurality of air ducts 1S are connected between the inside of the inner shell member 12 and the outer shell mem` ber 1 of the heater housing such that outside air may be permitted to pass radially into the hollow interior portion of the partitioning means. Thus, with insulation 19 below plate 10, upper insulation 17, and peripheral insulation 13, the inner metal surfaces of partitioning members 10, 12 and 16 need not be of high temperature resistant alloy to withstand the heating conditions inside of the heater chamber.

In theV present embodiment, the ducts 18 are spaced in four radial positions around the periphery of the heating chamber, with such ducts being in two horizontal planes and one duct superimposed above another in each of the four radial positions. This particular arrangement permits upward draft action and a cross tiow of air through the heating chamber with a resulting cooling of the inside of the hollow cylindrical inner shell 12. A larger number of small ducts may be used as hereinbefore noted, however, where the air ducts are staggered vertically, it' is necessary to have additional spacing between vertical tubes 7 to accommodate such ducts, or alternatively, it is necessary to utilize relatively small air ducts to minimize excessive radial spacing of the tubes 7.

In effecting the transfer of convection heat through the tube walls to the inner iiuid stream, it is desirable to increase heating eiciency by having a high velocity convection gas flow over the upper tube surfaces in the convection section, inasmuch as the heat transfer rate is proportional to the velocity of the heating stream. Although not shown in the drawing, it is desirable in a preferred embodiment to increase heat transfer rates by utilizing extended surface area to the tubes in the convection section by the use of a plurality of vertical ribs or staggered studs, and the like, around the upper portion of tubes 7. Thus, the inner shell member 12, with insulation 13, is positioned as close as possible to the upper portions of the tubes 7, so as to insure a high velocity flue gas rlow through the convection section 9. Also, in order to minimize turbulence, vertical partition-'= ing members 2G, with insulation 21, extend between upper andy lower air inlet tubes i8, so that the up-lowing iiue gas stream continues in a straight line path along the tubes 7 in the convection section 9 to the upper gas collection section 14.

Referring now to FIGURES 3 and 4 of the drawing, there is indicated a modied construction having three larger vertically elongated air ducts or passageways 22. Such air ducts extend from outside the exterior shell member 23, having internal insulation 24, to the hollow interior portion formed by the inner partitioning shells 25, having insulation 26. The latter together with the inside wall of the heater chamber from vertically elongated convection sections 27, which in turn accommodate the upper convection ends of tubes 28.

In a manner similar to that set forth and described in connectionl with FIGURES 1 and 2, the present embodiment positions the vertical tube members 28 around and adjacent to the inside wall of the heater chamber such that they may be exposed to high temperature radiant heat in a lower radiant heating section 29 and to high velocity hot convection gases in the elongated convection zones Z7. However, the upper ends of the tubes 28 are, in the present embodiment, indicated as having a multiplicity of circular studs 30 'to increase the heat absorption surface of each tub'fular member. A transverse partitioning member 31, with insulation 32, and extended sections 33 which connect with the outer shell 23 provide for the separation of the radiant section 29 and convection sections 27 within the interior of the heater chamber. The transverse partition 31 also supports the superimposed partitioning shell members 25 and an upper transverse closure member 34 having superimposed insulation 35. The construction thus provides open upper end portions to the convection 27 which communicate with the ilue gas plenum section 36 andr tlue gas outlet stack 37, while the central interior space between shell sections '25 is made substantially hollow and closed from the ue gas ow passing upwardly around the tubular members. A sloping conical shell section 41, with insulation 42, deiines the exterior of the gas collection section 36 and supports the stack 37.

The large elongated air ducts 22 have radial side plates 381 and side insulation 39 forming the side wall portions of the convection sections 27 land in eifect divide the upper portion of the heater into three separate convection sections 27 which are segments of an annulus. However, where the air duct openings 22 are less than the full height of the shell members 25, there may be interconnection of the segmental portions of the convection sections 27. For the purposes of the present application the terms annular or annular-form are used herein to describe the one or more narrow annular-shaped convection sections, whether continuous or separated into segments. Interconnection to effect a true annular zone permitting iiue gas flow 4from one adjacent section to the next is optional and not a requisite of the improved construction. In each modification of the improved heater construction there is, however, in elect, a hollow inner cylinderlike partitioning member, or cylindrical segments which define a hollowinterior central portion of `the heater and the inner wall, or wall portions, of the convection zone. In addition there is air duct means connecting from outside the heater tosuch hollow interior zone to provide cooling of the inside shell and preclude the necessity of high temperature resistant alloys.

It is not intended to limit the improved construction of the present invention to the use of any predetermined number of air duct means to the interior section or to any one vertical tube spacing arrangement and any tube bank design. A preferred design utilizes sufficient air duct passageways to provide cross ventilation and adequate interior cooling, although where desired one or more holes, such as apertures 40, may be located in the upper closure plate 34 and insulation 35 in order to provide some measure of draft action and inward iiow of air to the hollow section. It may further be pointed out that the embodiments hereinbefore described relate to cylindrical form updraft heaters; however, similar air duct arrangements in combination with an enclosed interior zone defining the interior Walls of one or more convection sections may be embodied with a box-type or rectangularly-shaped updraft heaters utilizing vertical tube arrangements along the walls of the heaters and vertically extended portions of wall tubes within the convection zones.

I claim as my invention:

1. A heater for iluid streams which comprises in combination, a confined vertically positioned heating chamber having a tine gas outlet stack from the upper end thereof, a plurality of vertically positioned Ifluid conduits positioned around and adjacent to the interior wall of said heating chamber, means connecting said conduits into at least one bank and fluid inlet and outlet means connecting thereto whereby iiuid may be passed through said conduits in said heater, heat supply means connecting with the lower end of said heating chamber, a transverse partitioning means extending across said chamber, hollovtr inner shell means superimposed on said partitioning means and positioned within the interior of said heating chamber, said partitioning means and inner shell means dividing such interior into a lower radiant heating section and an upper open-topped convection heating section, said superimposed shell means being positioned concentrically adjacent to and inwardly from the upper portions of said fluid conduits and forming thereby narrow gas passageway means in said convection section, an upper transverse closure member across the upper end of said inner shell means separating the hollow interior thereof from the top portion of said heating chamber and from flue gases passing therethrough from the yopen top of said convection section to said flue gas outlet stack, and air duct means extending radially through said convection section between the outside surface of said heating chamber and the interior of said hollow inner shell means whereby outside air is admitted to the interior of the latter.

2. A heater for fluid streams which comprises in combination, a coniined vertically positioned cylindrical heating chamber having a flue gas outlet stack from the upper end thereof, a plurality of vertically positioned iluid conduits positioned around and adjacent to the interior wall of said heating chamber, means connecting said fluid conduits into at least one bank and fluid inlet and outlet means connecting thereto whereby fluid may be passed through said conduits in said heater, burner means connecting with the lower end of said heating chamber and providing flame and hot combustion gases thereto, a transverse partition extending across said heating chamber, annular hollow inner shell means superimposed on said partition, said transverse partition and superimposed shell means dividing said heating chamber into a lower radiant heating section and an upper open-topped annularform convection heating section, said shell means being positioned concentrically adjacent to and inwardly from the upper portions of said fluid conduits and forming thereby narrow gas passageway means in said convection section, an upper transverse closure member across the upper end portion of said inner shell means and separating the hollow interior thereof from the top portion of said heating chamber and from resulting hue gases passing from said convection section to said gas outlet stack, a plurality of spaced air ducts extending through said convection section between the outside surface of said heating chamber and the interior of said hollow shell means, said ducts being spaced radially and vertically in a substantially uniform pattern whereby outside air is admitted to the interior of said shell means.

3. The heater `of claim 2 further characterized in that at least one opening is provided in the central portion of said upper transverse closure member permitting air flow to said flue gas outlet stack.

4. A heater for fluid streams which comprises in combination, a confined vertically positioned cylindrical heating chamber having a flue gas outlet stack from the upper end thereof, a plurality of vertically positioned fluid conduits positioned around and adjacent to the interior wall of said heating chamber, means connecting said iluid conduits into at least one bank and fluid inlet and outlet means connecting thereto whereby iiuid may be passed through said conduits in said heater, burner means connecting with the lower end of said heating chamber and providing flame and hot combustion gases thereto, a transverse partition extending across said heating chamber, annular hollow inner shell means superimposed on said partition, said transverse partition and superimposed shell means dividing said heating chamber into a lower radiant heating section and an upper open-topped annular-form convection heating section, said shell means being positioned concentrically adjacent to and inwardly from the upper portions of said iiuid conduits and forming thereby narrow gas passageway means in said convection section, an upper transverse closure member across the upper end portion of said inner shell means and separating the hollow interior thereof from the top portion of said heating chamber and from resulting ue gases passing from said convection section to said gas outlet stack, and vertically elongated air duct means spaced uniformly and extending radially through said convection section between the outside surface of said heating charnber and the interior of said hollow inner shell means, with said vertically elongated air duct means being open for substantially the full height of said convection section and of said inner shell means whereby outside' air is admitted to the interior of the latter.

References Cited in the tile of this patent UNITED STATES PATENTS 2,579,350 Weber Dec. 18, 1951 2,723,651 Bliss Nov. 15, 1955 2,737,159 McCarthy Mar. 6, 1956 

1. A HEATER FOR FLUID STREAMS WHICH COMPRISES IN COMBINATION, A CONFINED VERTICALLY POSITIONED HEATING CHAMBER HAVING A FLUE GAS OUTLET STACK FROM THE UPPER END THEREOF, A PLURALITY OF VERTICALLY POSITIONED FLUID CONDUITS POSITIONED AROUND AND ADJACENT TO THE INTERIOR WALL OF SAID HEATING CHAMBER, MEANS CONNECTING SAID CONDUITS INTO AT LEAST ONE BANK AND FLUID INLET AND OUTLET MEANS CONNECTING THERETO WHEREBY FLUID MAY BE PASSED THROUGH SAID CONDUITS IN SAID HEATER, HEAT SUPPLY MEANS CONNECTING WITH THE LOWER END OF SAID HEATING CHAMBER, A TRANSVERSE PARTITIONING MEANS EXTENDING ACROSS SAID CHAMBER, HOLLOW INNER SHELL MEANS SUPERIMPOSED ON SAID PARTITIONING MEANS AND POSITIONED WITHIN THE INTERIOR OF SAID HEATING CHAMBER, SAID PARTITIONING MEANS AND INNER SHELL MEANS DIVIDING SUCH INTERIOR INTO A LOWER RADIANT HEATING SECTION AND AN UPPER OPEN-TOPPED CONVECTION HEATING SECTION, SAID SUPERIMPOSED SHELL MEANS BEING POSITIONED CONCENTRICALLY ADJACENT TO AND INWARDLY FROM THE UPPER PORTIONS OF SAID FLUID CONDUITS AND FORMING THEREBY NARROW GAS PASSAGEWAY MEANS IN SAID CONVECTION SECTION, AN UPPER TRANSVERSE CLOSURE MEMBER ACROSS THE UPPER END OF SAID INNER SHELL MEANS SEPARATING THE HOLLOW INTERIOR THEREOF FROM THE TOP PORTION OF SAID HEATING CHAMBER AND FROM FLUE GASES PASSING THERETHROUGH FROM THE OPEN TOP OF SAID CONVECTION SECTION TO SAID FLUE GAS OUTLET STACK, AND AIR DUCT MEANS EXTENDING RADIALLY THROUGH SAID CONVECTION SECTION BETWEEN THE OUTSIDE SURFACE OF SAID HEATING CHAMBER AND THE INTERIOR OF SAID HOLLOW INNER SHELL MEANS WHEREBY OUTSIDE AIR IS ADMITTED TO THE INTERIOR OF THE LATTER. 